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On a length-biased life distribution based on the sinh-normal model
Antonio Sanhueza,Víctor Leiva,Esteban Flores 한국통계학회 2009 Journal of the Korean Statistical Society Vol.38 No.4
In this article, we characterize a new life distribution based on the sinh-normal model. Specifically, we find the density, the distribution function, and the moments of the new model. In addition, we carry out a brief graphical analysis of its density. Furthermore, we derive some properties and transformations related to the new distribution. Moreover, we conduct a study of its hazard rate. Finally, we present an example that illustrates the obtained results and a computational implementation of these results.
Oliva Manuel,Rubio Karol,Rivasplata Elder,Leiva Santos 한국곤충학회 2020 Entomological Research Vol.50 No.11
The coffee berry borer (CBB) is among the most harmful pests to coffee crops across the world, causing enormous harm to small‐ scale coffee farmers in northern Peru. This study aimed to contrast three different CBB control methods; cultural control (field sanitation), ethological control (red traps baited with ethanol–methanol (1:1)), biological control (use of the Beauveria sp., strain) and an integration of the aforementioned methods by comparing each control method’s efficiencies and CBB reduction percentage in coffee plantations located in the province of Rodriguez de Mendoza, Amazonas. Therefore, a completely randomized block design (CRBD) was applied. Subsequently, the results showed no statistical differences among treatments carried out in this study. However, high infestation reduction percentages of up to 70% were reached, evidencing the effect of these treatments. In addition, the final results were impacted by environmental conditions and population pressure.
Acinetobacter Prosthetic Joint Infection Treated with Debridement and High-Dose Tigecycline
Andrea Vila,Hugo Pagella,Claudio Amadio,Alejandro Leiva 대한감염학회 2016 Infection and Chemotherapy Vol.48 No.4
Prosthesis retention is not recommended for multidrug-resistant Acinetobacter prosthetic joint infection due to its high failure rate. Nevertheless, replacing the prosthesis implies high morbidity and prolonged hospitalization. Although tigecycline is not approved for the treatment of prosthetic joint infection due to multidrug resistant Acinetobacter baumannii, its appropriate use may preclude prosthesis exchange. Since the area under the curve divided by the minimum inhibitory concentration is the best pharmacodynamic predictor of its efficacy, we used tigecycline at high dose, in order to optimize its efficacy and achieve implant retention in 3 patients who refused prosthesis exchange. All patients with prosthetic joint infections treated at our Institution are prospectively registered in a database. Three patients with early prosthetic joint infection of total hip arthroplasty due to multidrug resistant A. baumannii were treated with debridement, antibiotics and implant retention, using a high maintenance dose of tigecycline (100 mg every 12 hours). The cases were retrospectively reviewed. All patients signed informed consent for receiving off-label use of tigecycline. Tigecycline was well tolerated, allowing its administration at high maintenance dose for a median of 40 days (range 30–60). Two patients were then switched to minocycline at standard doses for a median of 3.3 months in order to complete treatment. Currently, none of the patients showed relapse. Increasing the dose of tigecycline could be considered as a means to better attain pharmacodynamic targets in patients with severe or difficult-to-treat infections. Tigecycline at high maintenance dose might be useful when retention of the implant is attempted for treatment for prosthetic joint infections due to multidrug resistant Acinetobacter. Although this approach might be promising, off-label use of tigecycline should be interpreted cautiously until prospective data are available. Tigecycline is probably under-dosed for the treatment of implant and biofilm associated infections.
Francisco Ortiz-Navas,Juan Navarro-Gregori,Gabriel Leiva,Pedro Serna 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.4
This study extends previous experimental research on the shear behaviour of macrosynthetic fibre-reinforced concrete beams and compares them to steel fibre-reinforced concrete beams with similar mechanical and geometrical properties. This work employed two fibre types: 60/0.9 (long/diameter) double hooked-end steel fibre and 60/85 monofilament polypropylene fibre. Beams were tested by shear loading covering parameters, such as two different cross-section widths, two shear-span-to-effective-depth ratios, two fibre types and using repetitions with and without transverse reinforcement. For quantitative comparison purposes, crack pattern evolution was studied along increasing loads levels. Effects were studied by photogrammetry, including influence of fibres on crack propagation in uncracked and dowel zones, influence of fibres on stirrup behaviour, and shear deformation or kinematics of critical shear cracks. The results evidenced similar effectiveness for both fibre types in controlling shear crack propagation and horizontal dowel cracking. Both fibres provided similar shear ductility and shear deflections. Consequently, the authors confirm that residual flexural tensile strengths are a convenient parameter for characterising the shear behaviour of fibre-reinforced concrete beams.
Sebastián Contreras-Fernández,Lennin Florez-Leiva,María Camila Bernal-Sánchez,Wilberto Pacheco-Paternina,Shalenys Bedoya-Valestt,Lorenzo Portillo-Cogollo 한국해양과학기술원 2022 Ocean science journal Vol.57 No.4
Estuaries are highly diverse ecosystems that occur at the interface between land and sea and thus possess a high degree of environmental variation over short spatial and temporal scales. The Gulf of Urabá (1800 km 2; mean depth ~ 40 m) is a semiclosed estuarine area located in the southwestern part of the Caribbean Sea (South America). This large coastal–estuarine ecosystem operates as a biogeochemical reactor due to it featuring examples of high nutrient concentrations on the surface (NO 3- = 1619 μM; NO 2- = 0.505 μM; NH 4+ = 2.938 μM; PO 4 3- = 7.603 μM), high Chl α (max = 30.17; min = 0.02; mean = 9 mg m−3), as well as blooms of toxic algae, mostly Pseudo-nitzschia pseudodelicatissima. An outbreak of Tripos fusus causes bioluminescence and about 20 events of hypoxia (< 2–4 mg O 2 L−1) within a time series of 10 years. Despite this, information regarding the biological and biogeochemical oceanography (chlorophyll α, biomass, planktonic composition, nutrient cycling, mass balance of elements, and interannual variability) remains non-existent. Therefore, elucidating an ecosystem’s thresholds for various features is necessary for managing marine ecosystems, and especially for climate change projections. We here present a review of the functioning of this estuary, evaluating and reviewing each aspect of oceanographic variability.
"Beach Lifeguards' Sun Exposure and Sun Protection in Spain"
de Troya Martin, Magdalena,Sanchez, Nuria Blazquez,Garcia Harana, Cristina,Leiva, Ma Carmen Alarcon,Arjona, Jose Aguilera,Ruiz, Francisco Rivas,de Galvez Aranda, Ma Victoria Occupational Safety and Health Research Institute 2021 Safety and health at work Vol.12 No.2
Background: Sunburn is the main avoidable cause of skin cancer. Beach lifeguards spend many hours exposed to the effects of solar radiation during their work day, precisely at times of the year when levels of solar irradiation are highest. The aim of this study is to quantify the risk to beach lifeguards of sun exposure. Methods: A descriptive cross-sectional study was carried out in the Western Costa del Sol, southern Spain, during the summer of 2018. The research subjects were recruited during a skin cancer prevention course for beach lifeguards. All participants were invited to complete a questionnaire on their habits, attitudes, and knowledge related to sun exposure. In addition, ten were specially monitored using personal dosimeters for three consecutive days, and the results were recorded in a photoprotection diary. A descriptive analysis (mean and standard deviation for the quantitative variables) was performed, and inter-group differences were evaluated using the Mann-Whitney U test. Results: Two hundred fifteen lifeguards completed the questionnaire, and 109 met the criteria for inclusion in this analysis. The mean age was 23.8 years (SD: 5.1), 78.0% were male, 71.5% were phototype III or IV (Fitzpatrick's phototype), and 77.1% had experienced at least one painful sunburn during the previous summer. The mean daily personal ultraviolet exposure per day, the minimal erythema dose, and the standard erythema dose, in J/m<sup>2</sup>, were 634.7 [standard deviation (SD): 356.2], 2.5 (SD: 1.4) and 6.35 (SD: 3.6), respectively. Conclusion: Beach lifeguards receive very high doses of solar radiation during the work day and experience correspondingly high rates of sunburn. Intervention strategies to modify their sun exposure behavior and working environment are necessary to reduce the risk of skin cancer for these workers and to promote early diagnosis of the disease.
Dávalos Enrique,Enciso José-Luis,Silva Nicolás,Pinto-Ríos Juan,Leiva Ariel 한국통신학회 2023 ICT Express Vol.9 No.5
Bandwidth fragmentation is a critical problem for Elastic Optical Networks (EON), and spectrum defragmentation is the most important strategy to mitigate this phenomenon. In this work we propose a Machine Learning (ML) based method for estimating the Blocking Rate, which, when exceeding a threshold, triggers a defragmentation process. This is done in order to achieve better results in terms of the number of blocking demands and the number of re-routed connections. The performance of the proposed method was compared with two other known strategies: fixed-time (FT) defragmentation, and triggering based on one fragmentation metric (BFR). Simulation results were evaluated using two multi-objective metrics. Experimental results show that the proposed method is more efficient than the other two, being the best method in 85.7% of comparisons using the Pareto Coverage metric, and obtaining 47.4% of non-dominated solutions in the Pareto Front.